Various methods are available to analyze biological samples using optical analyses, including reflective and transmitted light, fluorescence, and luminescence. The purpose of the analysis is often to assay the response of cells, for example, to the presence of a chemical (e.g., a nutrient, hormone, antibiotic, pharmaceutical, toxic chemical, etc.).
However, methods and devices in use to date are generally limited in terms of their mechanical reliability, easy of use, capacity, speed, expense, and format flexibility. For example, devices currently in use are only capable of monitoring certain, specific formats, and are not capable of being adapted for use with multiple formats such as various microtiter plates (e.g., 96-, 384-, and 1536-well plates) or petri plates. All existing readers read one multiwell assay plate at a time. In addition, most or all available readers have an optical system which reads one row of a multiwell test panel at a time. Some examples of instruments that incubate and read a large number of multiwell plates are the Vitek (See e.g., 5,762,873, 5,853,667, 5,853,666, 5,798,085, 5,798,084, 5,670,375, 5,843,380, 5,766,553, D382,647, 5,697,409), MicroScan, and Sensititre instruments. The Vitek and MicroScan instruments have complex mechanisms for sliding out each plate, one at a time, for reading, and then sliding it back onto its shelf, while Sensititre has a single reading station, with an elevator transport system that moves each plate, one at a time, first onto the elevator, then to the reading station, and then back to its shelf. While these features allow for the analysis of multiple plates, the mechanisms are inefficient and are not capable of use with multiple formats. Thus, a need exists for improved instruments that increase mechanical reliability, easy of use, capacity, speed, affordability, and flexibility with multiple formats.